畸变产物耳声发射测试对噪声性聋诊断的敏感度和特异度

目的 探讨畸变产物耳声发射测试对噪声性聋的诊断价值。方法 对115名军人（204耳）进行DPOAE幅值测试,采用两个等强度L1＝L2＝70dB SPL的纯音信号f1、f2＝1．2。测试1、2、4kHz和6kHz DPOAE幅值,根据DPOAE幅值是否大于或小于标准值,判断听力正常与否。并同纯音听阈进行对照。结果 1、2、4和6kHz各频率的敏感度分别是70％、67％、85％和73％;特异度分别是71％、66％、84％和75％。结论 DPOAE幅值测试用于诊断噪声性聋,缺乏足够的敏感性和特异性,单一的DPOAE幅值测试,不能诊断噪声性聋。     

畸变产物耳声发射与纯音听阈间测试频率的相关性研究

目的探讨畸变产物耳声发射(DPOAE)测值与纯音听阈值之间的相关性，阐明DPOAE测试频率(f0)与纯音听阈测试频率之间的对应关系。方法选正常听力人20倒(40耳)，蜗性聋病人100例(179耳)进行纯音听阈和DPOAE测试。用相关分析的统计方法计算出DPOAE测值与纯音听阈值之间的相关系数。结果DPOAE测值与纯音听阈值之间有负相关关系。f0为0．5、0．75、1．0．1．5、2．0、3．0、4．0、6．0、8．0kHz时的DPOAE测值与测试频率分别为1．0、1．0、1．0、2．0．3．0、3．0、4．0、6．0、8．0kHz时的纯音听阈值之间有相对最大的负相关系数。f0为0．5、0.75、1．0、1．5、2．0、3．0、4．0、6．0、8．0kHz时所对应的量相关纯音听阈测试频率分别为0．75、1．0、1．5、2．0、2．5、3．5、5．0、6．0、8．0kHz。结论DPOAE测值与纯音听阈值之间有负相关关系，且DPOAE测试频率与纯音听阈测试频率间存在一定的对应关系。     

畸变产物耳声发射对耳蜗性聋和耳蜗后性聋的鉴别诊断意义

目的 探讨畸变产物耳声发射（DPOAE）鉴别诊断耳蜗性聋和耳蜗后性聋的意义。方法 采用ILO96耳动态分析仪对49例耳蜗性聋和4例耳蜗后性聋进行DPOAE测试。结果 耳蜗性聋组的DPOAE图显示出DPOAE幅值随纯音听阈的升高有不同程度的下降,并显示出很好的频率特异性,当纯音听阈＞50dBHL时,DPOAE消失。耳蜗后性聋组的DPOAE图显示出的DPOAE幅值变化不明显,仍在正常范围,与纯音听阈长吭程度缺乏相对应关系。结论 DPOAE是一种有效的辅助性鉴别诊断耳蜗性聋和耳蜗后性聋的方法。     

畸变产物耳声发射与纯音听阈间测试频率的相关性研究

目的:探讨畸变产物耳声发射(OPOAE)测值与纯音听阈值之间的相关性,阐明DPOAE测试频率(f0)与纯音听阈测试频率之间的对应关系。方法:选正常听力人20例(40耳),蜗性聋病人100例 (179耳)进行纯音听阈和DPOAE测试。用相关分析的统计方法计算出DPOAE测值与纯音听阈值之间的相关系数。结果:DPOAE测值与纯音听阈值之间有负相关关系。f0为0．5、0．75、1．0、1．5、 2．0、3．0、4．0、6．0、8．0kHz时的DPOAE测值与测试频率分别为 1．0、1．0、1．0、2．0、3．0、3．0、4．0、6．0、8．0kHz时的纯音听阈值之间有相对最大的负相关系数。f0为0．5、0．75、1．0、1．5、 2．0、3．0、4．0、6．0、8．0kHz时所对应的最相关纯音听阈测试频率分别为0．75、1．0、1．5、2．0、2．5、3．5、5．0、6．0、8．0kHz。结论:DPOAE测值与纯音听阈值之间有负相关关系,且DPOAE测试频率与纯音听阈测试频率间存在一定的对应关系。图1表3参6     

畸变产物耳声发射幅值与纯音听阈相关性的研究

目的：探讨畸变产物耳声发射（distortion product otoacoustic emissions,DPOAE）与常规纯音测听及扩展高频测听的关系。方法：对耳科正常人进行0．5－16kHz DPOAE、常规纯音测听及扩展高频测听检查，比较DPOAE和常规纯音测听、扩展高频测听结果的相关性。结果：0．5-3kHz DPOAE幅值与扩展高频区（10－12．5kHz）的纯音听阈相关；4－6kHz DPOAE幅值与相应频率及11．2kHz的纯音听阈相关；11．2kHz DPOAE幅值与4KHz纯音听阈明显相关。结论：DPOAE可能不全来源于对应频率区及较高频率区耳蜗外毛细胞，其产生部位和机制尚需深入研究。     

水杨酸钠急性注射对清醒豚鼠畸变产物耳声发射的影响

目的研究急性注射水杨酸钠对清醒豚鼠畸变产物耳声发射（DPOAE）的影响及其特征，探讨其对外毛细胞（OHC）的毒性作用。方法采用CELESTA 503型耳声发射分析仪在清醒豚鼠上记录DPOAE（包括DP听力图及DP输入／输出函数曲线）来监测水杨酸钠对耳蜗及毛细胞功能的影响；急性水杨酸钠实验组及生理盐水对照组分别在注药前及注药后2、4、8h进行DPOAE测试；测试结果采用SPSS10．0统计软件进行分析。结果急性水杨酸钠注射主要引起DPOAE幅值和I／O斜率分别可逆性下降和升高，注射后2h变化最大，8h基本恢复；某些频率或强度的DPOAE幅值、I／O斜率在注药后与注药前结果有统计学差异（P〈0．01或P〈0．05），特别是8kHz。结论DPOAE幅值和I／O斜率分别叮逆性下降和升高表明OHC能动性下降，即耳蜗OHC功能改变为其耳毒性作用之一。     

对感音神经性聋的几种耳声发射观察

采用耳动态分析仪ILO－92对369例感音神经性聋患者进行了畸变产物耳声发射（DPOAE）、瞬态诱恨性耳声发射（TEOAE）和自发性耳声发射（SOAE）测试。结果表明：DPOAE可以准确地反映患耳相应的频率损失范围，其出率和幅值与主观听阈水平有关。对所有患耳均进行了SOAE测试，检出率为9.4%，低于听力正常人49％的检出率；其中蜗后性听力损失耳的SOAE检出率为100％。由于任何早期的耳蜗病理变化均可对OAE作出反应，故它可对感音神经性听力下降患者的耳蜗功能作出早期预测和评估。     

单侧耳聋配戴助听器后健侧耳DPOAE幅值增高

目的：通过给单侧聋耳配戴助听器后对健侧耳影响的客观观察，探讨单侧耳聋配戴助听器的必要性。方法：对27例单侧耳聋对侧耳听阈正常的患者进行患耳配戴助听器前后的耳声发射检测。首诊分别行纯音听阈和健耳DPOAE检测，根据患侧听力损失程度分中、重度两组，之后为其配戴及调试助听器，并在一个月、三个月及六个月后再行耳声发射检测。对照组13例单侧耳聋发病时对侧耳听力正常，首诊行双耳纯音听阈测试和对侧耳耳声发射检测，但未配 戴助听器。结果：中度耳聋组19耳健侧DPOAE幅值较低，仅有4耳尚在正常范围的低值内，另外15耳低于正常范围。为其配戴助听器后行耳声发射的动态观察，发现DPOAE幅值较配戴助听器前明显提高，其中三个月后幅值提高最明显。六个月后的平均幅值为8．4dB SPL/500Hz、11．2dB SPL/1kHz、10．4dB SPL/2kHz，t检验与配戴助听器前比较有高度显著性差异（P＜0．01），DPOAE I／O示非线性机制较好，重度聋组8耳DPOAE幅值低于正常范围，配戴助听器后5耳DPOAE幅值提高较小,t检验与配戴助听器前比较有显著差异（P＜0．05），另外3耳未见明显改善。对照组13例分别在首次就诊及半年后行纯音听力测试及耳声发射检查，原健耳纯音听阈逐渐升高，为33－55dB HL，未引出DPOAE及DPOAE I／O函数曲线。结论：单侧耳聋配戴助听器经过一段时间后出现听力损失的对侧耳听阈出现不同程度的改善。单侧耳聋久之如不及时进行 康复干预，必将导致健侧耳功能失代偿而使该耳听阈升高。     

听力正常耳鸣与诱发性耳声发射的关系

目的:分析听力正常的耳鸣患者的耳蜗功能,探讨耳鸣的客观检查手段。方法:对听力正常的单侧 耳鸣患者50例(50耳,耳鸣1组)、听力正常的双侧耳鸣患者23例(46耳,耳鸣2组)和正常人34例(68耳,对照 组)进行瞬态诱发耳声发射(TEOAE)和畸变产物耳声发射(DPOAE)。耳鸣1、2组同时进行耳鸣频率匹配检查, 并分析在TEOAE及DPOAE测试结果中有无相应表现。结果:①TEOAE通过率,耳鸣1组为64.0%,耳鸣2组 为91.3%,对照组为100%(1组P<0.01,2组P>0.05);②DPOAE通过率,3组均为100%;但耳鸣1组在 3.125kHz及8.837kHz的波幅均值较对照组低,两组差异具有统计学意义(P<0.05);③耳鸣音调分布为0.25 ～8.00kHz。在TEOAE频谱中及DPOAE听力图中,部分耳表现出与匹配频率相对应的低反应峰或频率成分 缺失以及低幅值。结论:部分听力正常的耳鸣患者已有耳蜗毛细胞的损害;TEOAE及DPOAE可以作为外周性 耳鸣诊断的一种客观检测方法;前者对耳蜗性耳鸣的早期诊断敏感而直观,而后者适用于耳鸣的频率分析。     

母系遗传性聋家系的纯音测听及畸变产物耳声发射测试的相关分析

目的：探讨母系遗传非综合征性聋的听力学特征及畸变产物耳声发射测试对其听改变早期诊断的优越性。方法：对六个母系遗传家系成员共102人进行纯音测听、DPOAE评估其听力，比较纯音测听与DPOAE检测耳蜗早期病变的灵敏性。结果：纯音测听为感音神经性聋的38例中，PTA≥45d B HL的18例，DPOAE反应缺失；PTA＜45dB HL的20例，DPOAE高频或高、中频振幅下降或缺失；纯音测听正常者中4例DPOAE显示高频或高中频振幅下降。结论：母系遗传非综合征性聋的听力损害为双侧、对称性、进行性感音神经性聋，早期表现高频损害，DPOAE可在纯音听阈改变之前，发现早期耳蜗轻微的病理变化，对早期诊断及遗传咨询有较大指导意义。     

畸变产物耳声发射与响度重振现象关系的探讨

目的 探讨响度重振与耳蜗主动机制异常之间的关系，为耳声发射用于诊断耳蜗性病变提供更多指标。方法 通过对２０例（４０耳）健康人、５０例（６３耳）常规重振检测频率阳性者和１１例（１５耳）蜗后性聋耳进行畸变产物耳声发射（ｄｉｓｔｏｒｔｏｎ ｐｒｏｄｕｃｔ ｏｔｏａｃｏｕｓｔｉｃ ｅｍｉｓｓｉｏｎ，ＤＰＯＡＥ）的输入－输出（Ｉ／Ｏ）曲线的测试和分析。结果 重振检测阳性患耳不同频率ＤＰＯＡＥ的Ｉ／Ｏ曲线斜率     

A validation and potential clinical application of multivariate analyses of distortion-product otoacoustic emission data

OBJECTIVE: To test the generalizability of multivariate analyses of distortion-product otoacoustic emission (DPOAE) data. Previously published multivariate solutions were applied to a new set of data to determine if test-performance improvements, evident in previous reports, are retained. An additional objective was to provide an alternative approach for making multivariate dichotomous decisions of hearing status in the clinic, based on DPOAE measurements. DESIGN: DPOAE level and noise were obtained in 345 ears of 187 subjects. Approximately one third of the subjects had normal hearing, whereas the remainder had hearing loss, ranging from 25 to more than 120 dB HL. DPOAE data were collected at each of nine frequencies. After data collection, clinical decision theory, in combination with univariate (DPOAE level and signal-to-noise ratio [SNR]) and multivariate (logistic regression) analyses, was used to construct relative operating characteristic (ROC) curves and to generate ROC curve areas. In addition, test performance was assessed by fixing the false-alarm rate and comparing different approaches to analyses in terms of their failure rates as a function of magnitude of hearing loss. The DPOAE test results were compared with either single-frequency or multifrequency gold standards. The multivariate solutions were taken from previously published work (Dorn et al., 1999; Gorga, et al., 1999). RESULTS: DPOAE level and SNR resulted in roughly equivalent test performance (ROC curve areas and failure rates among ears with hearing loss), although DPOAE level performed better for frequencies above 1 kHz, and SNR performed better for frequencies at 0.75 and 1 kHz. Multivariate analyses resulted in better test performance for nearly all conditions, compared with the univariate approaches that used either DPOAE level or SNR. The improvements in test performance were greatest for the frequencies at which the univariate analyses performed poorest (0.75 kHz, 1 kHz, and 8 kHz). Less difference was observed between univariate and multivariate approaches when multifrequency gold standards were used; however, even for the multifrequency cases, multivariate analyses generally resulted in better performance. An approach that might facilitate the interpretation of multifrequency DPOAE measurements in the clinic is described. CONCLUSIONS: Previously described multivariate analyses were robust in that they improved test performance when applied to an entirely new set of DPOAE data. This, in turn, suggests that the previously described multivariate solutions may have clinical utility in that they are expected to improve test performance at no additional cost in terms of data-acquisition or data-analysis time. In addition to demonstrating that these solutions generalized to new data, an alternative approach to interpreting multifrequency DPOAE measurements is provided that includes the advantages of using multivariate analyses. This new metric may be useful when DPOAEs are used for screening purposes.     

畸变产物耳声发射与响度重振现象关系的探讨

目的探讨响度重振与耳蜗主动机制异常之间的关系，为耳声发射用于诊断耳蜗性病变提供更多指标。方法通过对２０例（４０耳）健康人、５０例（６３耳）常规重振检测频率阳性者和１１例（１５耳）蜗后性聋耳进行畸变产物耳声发射（ｄｉｓｔｏｒｔｉｏｎｐｒｏｄｕｃｔｏｔｏａｃｏｕｓｔｉｃｅｍｉｓｉｏｎ，ＤＰＯＡＥ）的输入－输出（Ｉ／Ｏ）曲线的测试和分析。结果重振检测阳性的患耳不同频率ＤＰＯＡＥ的Ｉ／Ｏ曲线斜率的均值与健康人对应频率Ｉ／Ｏ曲线斜率的均值相比明显增大（Ｐ＜０．０１），其ＤＰＯＡＥ的检测阈也明显提高。结论响度重振与耳蜗主动机制异常有特定联系，ＤＰＯＡＥ的Ｉ／Ｏ曲线对耳蜗主动机制的评价更直观、准确，可能成为一种有价值的诊断耳蜗性病变的指标。     

Utility of OAE screener (GSI 70) for the evaluation of distortion product otoacoustic emissions

The purpose of this study was to investigate the ability of the OAE screener GSI 70 to evaluate of cochlea function in neonates, infants and adults. Distortion product otoacoustic emissions (DPOAEs) were measured using the GSI 70 DPOAE Analyzer and evaluated in 123 human ears between December 1999 and June 2000. We performed the following four general clinical tests to determine the reliability of the GSI 70: 1) comparison of DPOAE levels measured using the ILO 92 and the GSI 70 in 55 adult ears, 2) comparison of DPOAE levels measured using the GSI 70 and hearing levels in 55 adult ears, 3) comparison of DPOAE levels measured using the GSI 70 and ABR levels in 45 neonate and infant ears, and 4) evaluation of the utility of DPOAE measurements obtained using the GSI 70 in functional deafness cases. The following results were obtained: 1) DPOAE levels measured with the ILO 92 and the GSI 70 were closely correlated (correlation coefficient, 0.773 at 2 kHz and 0.813 at 4 kHz). 2) The sensitivity of the GSI 70 in adult ears confirmed to have normal hearing was 80% at 2 kHz and 100% at 4 kHz; the specificity of hearing-impaired ears was 94% at 2 kHz and 94% at 4 kHz. 3) The sensitivity of the GSI 70 in normal neonate and infant ears with normal hearing was 100% at 2 kHz and 100% at 4 kHz; the specificity of hearing-impaired neonate and infant ears was 97% at 2 kHz and 94% at 4 kHz. 4) All of the functionally deaf ears showed excellent DPOAE responses. Examinations using the GSI 70 DPOAE analyzer were very easy and fast. Also, the results were highly reliable, with the exception of one adult who was classified as having normal hearing in an out-of-scale hearing level at 2 kHz. We suggest that specific criteria be established for the clinical usage of the GSI 70 in performing objective hearing evaluations.     

单侧突发性聋患者对侧耳耳声发射分析

目的研究突发性聋患者单耳发病时对侧耳的耳蜗功能状态。方法利用Capella耳声发射仪对单侧突发性聋患者的对侧耳50例(50耳,病例组)及正常人30例(60耳,对照组)分别进行瞬态声诱发耳声发射(TEOAE)及畸变产物耳声发射(DPOAE)检测,记录和分析TEOAE的通过率及各频率DPOAE的检出率、幅值。结果①TEOAE通过率对照组为100%,病例组为75%,两组比较差异有统计学意义(χ2=20.84,P<0.01);②DPOAE检出率在0.5、0.75、1.0、3.0、4.0 kHz频点上,病例组低于对照组(P<0.05或P<0.01);③与对照组相比,病例组各频率DPOAE的幅值均降低,差异有统计学意义(P<0.05或P<0.01)。结论部分突发性聋患者的对侧耳已出现早期耳蜗功能受累,利用耳声发射分析方法可在听力损失出现之前早期发现此类病变。     

Distortion product otoacoustic emission test performance for a priori criteria and for multifrequency audiometric standards.

OBJECTIVES: 1) To describe distortion product otoacoustic emission (DPOAE) test performance when a priori response criteria are applied to a large set of DPOAE data. 2) To describe DPOAE test performance when multifrequency definitions of auditory function are used. 3) To determine DPOAE test performance when a single decision regarding auditory status is made for an ear, based on DPOAE data from several frequencies. 4) To compare univariate and multivariate test performance when multifrequency gold standard definitions and response criteria are applied to DPOAE data. DESIGN: DPOAE and audiometric data were analyzed from 1267 ears of 806 subjects. These data were evaluated for three different frequency combinations (2, 3, 4 kHz; 2, 3, 4, 6 kHz; 1.5, 2, 3, 4, 6 kHz). DPOAE data were collected for each of the f2 frequencies listed above, using primary levels (L1/L2) of 65/55 dB SPL and a primary ratio (f2/f1) of 1.22. Sensitivity and specificity were evaluated for signal to noise ratios (SNRs) of 3, 6, and 9 dB, which are in common clinical use. In addition, test performance was evaluated using clinical decision theory, following the convention we have used in previous reports on otoacoustic emission test performance. Both univariate and multivariate analyses techniques were applied to the data. In addition to evaluating DPOAE test performance for the case when audiometric and f2 frequency were equal, multifrequency gold standards and multifrequency criterion responses were evaluated. Three new gold standards were used to assess test performance: average pure-tone thresholds, extrema thresholds that took into account both the magnitude of the loss and the number of frequencies at which hearing loss existed, and a combination of the two. These new gold standards were applied to each of the three frequency groups described above. RESULTS: As expected, SNR criteria of 3, 6, and 9 dB never resulted in perfect DPOAE test performance. Even the most stringent of these criteria (9 dB SNR) did not result in a sensitivity of 100%. This result suggests that caution should be exercised in the interpretation of DPOAE test results when these a priori criteria are used clinically. Excellent test performance was achieved when auditory status was classified on the basis of the new gold standards and when either SNR or the output of multivariate logistic regressions (LRs) were used as criterion measures. Invariably, the LR resulted in superior test performance compared with what was achieved by the SNR. For SNR criteria of 3, 6, and 9 dB and (by definition) for the LR, specificity, in general, exceeded 80% and often was greater than 90%. Sensitivity, however, depended on the magnitude of hearing loss. Diagnostic errors, when they occurred, were more common for patients with mild hearing losses (21 to 40 dB HL); sensitivity approached 100% once the hearing loss exceeded 40 dB HL. The largest differences between test performance based on SNR or LR occurred for the ears with mild hearing loss, where the LR resulted in more accurate diagnoses. CONCLUSIONS: It should not be assumed that the use of a priori response criteria, such as SNRs of 3, 6, or 9 dB, will identify all ears with hearing loss. Test performance when multifrequency gold standards are used to define an ear as normal or impaired and when data from multiple f2 frequencies are used to make a diagnosis, resulted in excellent test performance, especially when the LR was used. When predicting auditory status with multifrequency gold standards, the LR resulted in relative operating characteristic curve areas of 0.95 or 0.96. An output from the LR can be selected that results in a specificity of 90% or better. When the loss exceeded 40 dB HL, the same output from the LR resulted in test sensitivity of nearly 100%. These were the best test results that were achieved. (ABSTRACT TRUNCATED)     

噪声暴露工人畸变产物耳声发射和扩展高频测听的研究

目的 :分析畸变产物耳声发射 (DPOAE)和常频纯音测听、扩展高频测听的关系 ,借以探讨DPOAE的产生机制以及在噪声性听力损伤的监测和早期诊断中的应用价值。方法 :对 4 2例耳科正常人 (对照组 )和 2 0例噪声暴露工人 (实验组 )进行 0 .5～ 16 .0kHzDPOAE、常频纯音测听及扩展高频测听的检测 ,比较对照组和实验组DPOAE和常频纯音测听、扩展高频测听的结果。结果 :实验组纯音听阈在 6 .0kHz处和扩展高频区下降明显 ,与对照组比较 ,差异有显著性意义 (P <0 .0 5 ) ;DPOAE幅值在 4 .0、6 .0和 11.2kHz处下降明显 ,与对照组比较 ,差异均有显著性意义 (P <0 .0 5 ) ;而在 12 .5、14 .0、16 .0kHz 3个频率处两组差异无显著性意义 (P >0 .0 5 )。结论 :常频DPOAE检查可用于噪声性聋的早期诊断和监测。DPOAE可能来源于对应频率区及较高频率区耳蜗外毛细胞 ,其产生部位和机制尚待深入研究     

Clinical relevance of distortion product emissions by means of receiver operating characteristic (ROC) analysis.

The clinical use of distortion product otoacoustic emissions (DPOAE) stems from the observation that the outer hair cells are the most vulnerable part of the cochlea, and damage to these cells is associated with hearing loss and loss of DPOAE. The purpose of this study is to evaluate the applicability of DPOAE in predicting hearing thresholds under clinical conditions. DPOAE measurements (L1 = L2 = 70 dB SPL. f2/f1 = 1.20) of 219 hearing-impaired and normal hearing ears were analyzed. Recordings were acquired for DPOAE at 2 f1-f2 varying from 635 to 4052 Hz. The detectability of DPOAE in hearing-impaired subjects exhibited a strong hearing threshold dependence. Receiver operating characteristic (ROC) analysis yielded the highest sensitivity and specificity for threshold levels of about 30 dB at low frequencies and for threshold levels of about 60 dB at high frequencies. In addition, the separability of groups with different hearing status was more reliable at high frequencies as compared to low frequencies. The DPOAE provide an objective assessment of cochlear function. However, prognosis of hearing thresholds on the basis of DPOAE measurements depends strongly on the test frequency and is associated with large errors. Hence, the clinical use of DPOAE in predicting hearing thresholds is limited.     

畸变产物耳声发射甘油试验在内淋巴积水早期诊断中的价值

目的　用畸变产物耳声发射 (DPOAE)甘油试验来观察可疑梅尼埃病患耳内淋巴积水早期对耳蜗功能的影响。方法　对可疑梅尼埃病患者组 (4 0耳 )及正常组 (34耳 ) ,于服用甘油 1小时前后分别进行DPOAE测试。结果　正常组甘油试验前后比较DPOAE各频率点幅值及信噪比无明显变化 (P >0 .0 5 ) ;患者组甘油试验前后比较以 0 .5kHzDPOAE幅值及信噪比变化最为显著 (P <0 .0 5 )。与正常组比较 ,患者组DPOAE 0 .5kHz幅值和信噪比变化、1.0kHz信噪比变化明显提高 (P <0 .0 5 )。研究还发现DPOAE幅值变化与信噪比变化有一定的线性增长趋势。结论　畸变产物耳声发射甘油试验可为临床表现无听力下降的可疑梅尼埃病患者的早期诊断提供一定的客观依据 ;在分析耳声发射甘油试验结果时应重视信噪比的变化